What makes some people laugh instead of yell when hurt? I’m this way, I accidentally banged my leg just below my knee on a chair the other day, and even though it hurt immensely, I started laughing. It’s not as though it was funny, I’ve just always been this way. What would make someone do that, is it a nervous reaction, or can pain hit a certain nerve that triggers laughter somehow?
Part of the laugh response to pain is conditioning. If, subconsciously you think being in pain is somehow “wrong” you laugh to cover it.
Laughter does release endorphins which are pain relieving substances your body makes in response to pain and stress. Why laughter causes the response, I can’t tell you. Its a secret. :D. No, it isn’t, I just don’t know the answer. 
My S&M days confirmed to me that the difference between pain & pleasure is purely a socialogical one. I did no real “science” on it but it came as a matter of conditioning from a lesson taught to me by my cousin when I was very young: I had torn most of the skin from my legs in a tumble down a cliff. When I finally came to rest my cousin was sitting on a boulder laughing. Before I could even wonder why, he said in the most autharitorian vice I’ve ever heard:“You can cry right now if you want, but you’ll still be fucked up.” I chose to laugh along with my trusted friend & relative at my misfortune & pain, and inadvertently learned that “pain” and “pleasure” are the same sensation with different interpretations/expectations. Yeah, when I sprained my knee the first time I was scared and the sensation was not pleasant, but when it happened as a familiar sensation with no long-lasting effects I derived pleasure from it. Same goes for…other experiences…that give me extreme sensation.
OK. Maybe that makes me weird.
Thanks for the helpful replies! I don’t derive any pleasure from the laughing or the pain, but hey, everyone reacts a little differently. 